Henry s



(No Model.)

H. S. PRENTISS.

ELECTRIC 0AM.

310,417,742. Patented Dec. 24, 1889.

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- UNITED STATES PATENT OFFICE.

HENRY S. PRENTISS, OF NEWV YORK, N. Y.

ELECTRIC CAM.

SPECIFICATION forming part of Letters Patent No. 417,742, dated December 24, 1889.

Application filed May 10,1889. Serial No. 310,287. (No model.)

To aZZ whom it may concern.-

Be it known that I, HENRY S. PRENTIss, a citizen of the United States, residing at New York, in the county and State of New York, have invented certain new and useful Improvements in Electric Cams, of which the following is a specification.

The object of the invention is to provide a device having the nature of a cam which shall close an electric circuit but once in two revolutions of the shaft upon which the device is The invention is illustrated in the accompanying drawings, in which Figure 1 is a side View of a disk in which the invention is embodied with a portion of the cover cut away, and Fig. 2 is a sect-ion through the line 2 2 of Fig. 1.

The device may be fixed upon a shaft S by means of the set-screw s. Vithin the disk A is formeda continuous groove at, having its lowest portion, or portion nearest the periphery of A, at a. This groove contains a small portion of mercury m. In the position shown in Fig. 1 the device has just operated or performed the function required and is ready tobe carried forward for another operation. The groove a can be traced by the dotted lines in Fig. 1 throughout two complete turns or revolutions within the dislc If we suppose the shaft S is turning so as to carry the disk in the direction indicated by the arrow, it is evident that the mercury m will be carried or will run within the groove to in the direction shown by the small arrows. When the disk a has made one revolution, the mercury will stand in the groove (0 at the point a The groove at this point is at the back side of the disk, as shown in Fig. 2, and it passes, therefore, behind that portion of the groove which is shown at (L The continued revolution of the disk carries the mercury through that part of the groove shown at a and a and finally, at the end of the second revolution, will reach the portion marked a. A very slight additional motion allows the mercury to drop into the place a'that is, at the point from which it started. In falling down the perpendicular part of the groove just beyond a", the mercury envelops the two ends of a small wire w, which may be conveniently attached to the shaft, as shown, and this operation will close an electric circuit, of which the shaft may form a part, and the other terminal may be a spring pressing against the edge of the disk. The circuit may include any device which is required to be operated; hence it will be seen that the cam has been obliged to make two complete revolutions in order to close the circuit once.

The device is useful in many places, but is especially useful in a clock where some device, as a calendar, is desired to be set in operation once in twenty-four hours, and this device saves the necessity of adding a twentyfour-hour wheel to the clock.

It will of course be plainly seen that three or more turns or convolutions of the duct may be made in the same manner, in which case the operation of the device takes place but once in the number of turns of the shaft corresponding to the number of such convolutions.

I claim as my invention- 1. A disk or wheel having a closed duct or groove, which makes two complete turns or convolutions within said disk, a conduct-ingfiuid within said duct, and means, as the wires 10, whereby an electric circuit is closed by the passage of said fluid ata certain point in said duct.

2. The combination of the shaft S, the disk A, having the duct formed within it in two complete convolutions and closing upon itself, as shown, the mercury or conductingfluid, and the conducting-wires through which a circuit is closed by the passage of said mercury.

3. The combination of a shaft, a disk or wheel carrying a duct, which makes two complete convolutions and closing upon itself, a moving body within said duct, and means whereby an electric circuit is closed by the passage of said body through a certain predetermined part of said duct.

In testimony whereof I have hereunto subscribed my name this 9th day of May, A. D. 1889.

HENRY S. PRENTISS.

Witnesses:

DANL. W. Enenoonn, CAROLINE E. DAVIDSON. 

